The present application relates generally to an improved data processing apparatus and method and more specifically to mechanisms for using unique local unicast addresses in a global domain name server.
Internet Protocol version 6 (IPv6) is an Internet Protocol version which is designed to succeed IPv4. IPv6 is an Internet Layer protocol for packet switched internetworks. The main driving force for the redesign of the Internet Protocol is the foreseeable IPv4 address exhaustion. IPv6 has a vastly larger address space than IPv4 due to the use of a 128-bit address as opposed to the IPv4 addresses that use only 32 bits.
In December of 1995, the IPv6 RFC 1884, directed to an IPv6 addressing architecture, defined the address block fec0::/10 as site-local addresses that could be used within a “site” for private IPv6 networks. However, there was an insufficient definition of the term “site” which led to confusion over the resulting routing rules. Subsequently, in September 2004, RFC 3879 was published in which this site-local address range was deprecated and solutions to its problems were postulated. In October 2005, in RFC 4193, a unique local unicast (ULU) address block was defined for use in private IPv6 networks. Essentially the unique local unicast address (ULUA) block was defined to replace the site-local addresses. The IPv6 RFC 4193 is available at http://tools.ietf.org/html/rfc4193.
As specified in section 5 of the RFC 4193, the prefixes of ULUA addresses are not mathematically guaranteed to be unique. Thus, there is the possibility that, if such ULUA addresses were to be used as global addresses for routing between sites, a collision may occur. A collision is when more than one device uses the same address and as a result, routing of data packets may be made to an incorrect device. That is, for example, there is a small possibility that the same locally assigned IPv6 local address will be used by two different organizations both claiming to be authoritative. In this scenario, it is likely there will be a connection attempt to the closest host with the corresponding locally assigned IPv6 local address. This may result in connection timeouts, connection failures indicated by ICMP Destination Unreachable messages, or successful connections to the wrong host machine. As a result, the ULUA addresses are not added to global domain name servers (DNS's) and are not routable in the global IPv6 Internet, but instead are only routable within a private network or between a limited set of sites.